Root Zone LGR for script: Khmer (Khmr) | rz-lgr-6-khmer-script-23sep25-en

This document is mechanically formatted from the above XML file for the LGR. It provides additional summary data and explanatory text. The XML file remains the sole normative specification of the LGR.

Date | 2025-09-23
LGR Version | 6 (Root Zone LGR for the Khmer Script)
Language | und-Khmr (Khmer Script)
Scope | domain: "." (Root)
Unicode Version | 16.0.0

# Description

# Root Zone Label Generation Rules for the Khmer Script

## Overview

This file contains a set of Label Generation Rules (LGR) for the Khmer script for the Root Zone. For more details on this LGR and additional background on the script, see “Proposal for a Khmer Script Root Zone LGR” [Proposal-Khmer]. This file is one of a set of LGR files that together form an integrated LGR for the DNS Root Zone [RZ-LGR-6]. The format of this file follows [RFC 7940].

## Repertoire

In addition to the 71 code points according to Section 5, “Repertoire”, in [Proposal-Khmer], one additional code point was added in public comment. Two Khmer subscript consonant sequences have been defined, for a total of 74 repertoire elements. The repertoire only includes code points used by languages that are actively written in the Khmer script.

The repertoire is contained in [MSR-6], which is a subset of [Unicode 16.0.0].

As part of the Root Zone, this LGR includes neither decimal digits nor the HYPHEN-MINUS.

Repertoire Listing: Each code point or range is tagged with the script or scripts with which the code point is used and one or more other character categories. For each repertoire element, one or more references document sufficient justification for inclusion in the repertoire; see the “References” below. For code points in the repertoire, comments identify the language using the code point.

## Variants

This LGR defines two Khmer consonants as variants of each other in their subscript form only. This is captured by a variant relation between the two subscript sequences, which are listed explicitly in the repertoire. See Section 6, “Variants” in [Proposal-Khmer],

Variant Disposition: All variants are of type “blocked”, making labels that differ only by these variants mutually exclusive: whichever label containing either of these variants is chosen earlier would be delegated, while any other equivalent labels should be blocked. There is no preference among these labels.

This LGR does not define allocatable variants.

The specification of variants in the Root Zone LGR follows the guidelines in [RFC 8228].

## Character Classes

Consonants: When more than one consonant occur together in the onset of a grapheme cluster, the additional consonants are written in subscript form, joined with the first consonant in the sequence. In Unicode, this is indicated by preceding each additional consonant with U+17D2 ្ KHMER SIGN COENG. Some consonants have been given the tag “base-only”; these do not take subscript form. Consonants can have light or strong pronunciation indicated by two shifter signs; additionally there are six signs for phonological modifications as discussed below. See Section 5.2, “Consonants” in [Proposal-Khmer].

Independent vowels: These occur independently and cannot combine with any of the marks including dependent vowels and signs. The use of a subscript form, while defined in Unicode, is not supported here. See Section 5.2, “Independent Vowels” in [Proposal-Khmer].

Dependent vowels: The 16 dependent vowels included in the Khmer LGR have been further classified into three subcategories namely dependent vowel 1, dependent vowel 2 and dependent vowel 3, see below. Dependent vowels must follow a consonant, shifter or the Robat sign. They cannot occur independently. See Section 5.3, “Dependent Vowels” in [Proposal-Khmer].

Shifters: the character U+17C9 ៉ KHMER SIGN MUUSIKATOAN is used with a subset of first series consonants, code points from this subset have been given the tag “series-one”. The character U+17CA ៊ KHMER SIGN TRIISAP is used with subset of second series consonants and with U+1794 ប KHMER LETTER BA. Code points from this subset have been given the tag “series-two”. The two characters are collectively known as consonant shifters and have been given the tag “shifter”. See Section 5.5, “Shifters” in [Proposal-Khmer] and reference [210].

Robat: The character U+17CC ៌ KHMER SIGN ROBAT has been given the tag “robat”. It follows consonants but unlike other signs may be followed by a dependent vowel. See Sections 5.3, “Dependent Vowels” and 5.4, “Signs” in [Proposal-Khmer].

Sign (Bantoc): The character U+17CB ់ KHMER SIGN BANTOC is used with a subset of consonants, that subset has been given the tag “series-three”, see Section 5.4, “Signs” in [Proposal-Khmer] and reference [205].

Signs (Yuukalepintu and Samyoksannya): The character U+17C8 ៈ KHMER SIGN YUUKALEAPINTU is written after a consonant to indicate that it is to be followed by a short vowel and a glottal stop. The sign is used with all the consonants. The character U+17D0 ័ KHMER SIGN SAMYOKSANNYA is written above a consonant or a shifter to indicate that the syllable contains a particular short vowel. The sign is used with all the consonants or all the shifters. See Section 5.4, “Signs” in [Proposal-Khmer].

Signs (Nikahit and Reahmuk): The character U+17C6 ំ KHMER SIGN NIKAHIT is used with consonants and some dependent vowels. These dependent vowels have been given a tag “dependent-vowel-1” (see Sections 5.3 and 5.4 in [Proposal-Khmer]). The character U+17C7 ះ KHMER SIGN REAHMUK is used with consonants and some dependent vowels. These dependent vowels have been given a tag “dependent-vowel-2” (see Sections 5.3 and 5.4 in [Proposal-Khmer]).

Sign (Toandakhiat): U+17CD ៍ KHMER SIGN TOANDAKHIAT is written over a final consonant to indicate that it is unpronounced. It is used with all consonants or U+17B7 ិ KHMER VOWEL SIGN I. The latter has been given a tag “dependent-vowel-3”. See Section 5.4, “Signs” in [Proposal-Khmer].

Sign (Ahsda): U+17CF ៏ KHMER SIGN AHSDA is used to highlight certain consonants as being a discrete word. It can follow a subset of consonants, that subset has been given the tag “series-four”.

## Whole Label Evaluation (WLE) and Context Rules

### Default Whole Label Evaluation Rules and Actions

The LGR includes the set of required default WLE rules and actions applicable to the Root Zone and defined in [MSR-6]. They are marked with ⍟. The default prohibition on leading combining marks is equivalent to ensuring that a label only starts with a consonant or independent-vowel. The actions compute a label disposition based on WLE rules or variant mapping types.

### Khmer-specific Rules and Action

Rules provided in the LGR as described in Section 7 of [Proposal-Khmer] constrain possible labels so that they reasonably conform to Khmer syllable structure. These constraints are presented as context rules on the affected code points, except for the whole-label rule and associated action that enforce the limit on the number of consecutive subscripted consonants.

Two further rules have been added. One is to ensure that subscript RO is always at the end of a syllable because many fonts render an out-of-order subscript RO without any visual distinction. The other limits U+17CF ៏ KHMER SIGN AHSDA to follow ក ដ ន and ហ only.

For any rule that is not a pure context rule, a suitable action has been added that invalidates any label matching the rule.

Compared to Section 7 of [Proposal-Khmer], the context rules for the two shifters have been relaxed when following a subscripted consonant. This slightly increases the set of possible valid labels.

The rules are:

- Subscript-consonant — A rule that specifies allowable consonant sequence. See Section 7.2 in [Proposal-Khmer]
- Subscript-consonant-limit — A rule that limits the occurrence of subscript-consonant to two. In case of three, the associate action gives the label the disposition invalid. See Section 7.3 in [Proposal-Khmer]
- Coeng-after-subscript-ro — A rule that ensures that subscript RO is not followed by further subscript consonants
- Coeng-context — A context rule for 17D2 that requires a consonant before it and a consonant other than base-only after it. See Section 7.4 in [Proposal-Khmer]
- Follows-consonant-robat-shifter — A context rule for those code points that must follow a consonant, robat or shifter. See Section 7.5 in [Proposal-Khmer]
- Follows-series-two-or-subscript-consonant — A context rule for those code points that must follow series-two consonants or any consonant if subscripted. See Section 7.6 in [Proposal-Khmer]
- Follows-series-one-or-subscript-consonant — A context rule for those code points that must follow series-one consonants or any consonant if subscripted. See Section 7.7 in [Proposal-Khmer]
- Follows-consonant — A context rule for those code points that must always follow a consonant. See Section 7.8 in [Proposal-Khmer]
- Follows-consonant-shifter A context rule for those code points that must always follow a consonant or shifter. See Section 7.9 in [Proposal-Khmer]
- Follows-consonant-depvowel-1-shifter — A context rule for those code points that must follow consonant, shifter or dependent-vowel-1. See Section 7.10 in [Proposal-Khmer]
- Follows-consonant-depvowel-2-shifter — A context rule for those code points that must follow consonant, shifter or dependent-vowel-2. See Section 7.11 in [Proposal-Khmer]
- Follows-series-three — A context rule for those code points that must follow series-three consonants. See Section 7.12 in [Proposal-Khmer]
- Follows-series-four — A context rule for those code point that must follow series-four consonants
- Follows-consonant-or-vowel-i — A context rule for those code points that must follow a consonant or 17B7 KHMER VOWEL SIGN I. See Section 7.13 in [Proposal-Khmer]

## Methodology and Contributors

The Root Zone LGR for the Khmer Script was developed by the Khmer Generation Panel. For details on methodology and contributors, see Sections 4 and 8 in [Proposal-Khmer], as well as [RZ-LGR-6-Overview].

### Changes from RZ LGR-5

A WLE rule and action were added in RZ LGR-6 to ensure subscript RO only occurs at end of a syllable because many fonts will not render an incorrectly placed one, which is a security risk. This may affect the validity of labels if they contain a misplaced subscript RO. A similar rule is not needed for subscript MO, due to distinct rendering.

The context rules for the shifters are adjusted to allow them to occur after any subscript consonant, not only one of their corresponding series. This slightly increases the set of valid labels.

Following public comment, the character U+17CF ៏ KHMER SIGN AHSDA was added to the repertoire with a context rule. This character occurs in few words, but they are very common. This increases the set of valid labels.

For the prior version see [RZ-LGR-5-Khmr].

## References

The following general references are cited in this document:

[MSR-6]
  Integration Panel, “Maximal Starting Repertoire — MSR-6 Overview and Rationale”, 23 September 2025,
  https://www.icann.org/en/system/files/files/msr-6-overview-23sep25-en.pdf
[Proposal-Khmer]
  Khmer Generation Panel, “Proposal for Khmer Script Root Zone LGR”, 15 August 2016,
  https://www.icann.org/en/system/files/files/proposal-khmer-lgr-15aug16-en.pdf
[RFC 7940]
  Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
  https://www.rfc-editor.org/info/rfc7940
[RFC 8228]
  A. Freytag, “Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels”, RFC 8228, August 2017,
  https://www.rfc-editor.org/info/rfc8228
[RZ-LGR-5-Khmr]
  ICANN, Root Zone Label Generation Rules for the Khmer Script (und-Khmr), Version 5, 26 May 2022 (XML)
  https://www.icann.org/sites/default/files/lgr/rz-lgr-5-khmer-script-26may22-en.xml
  non-normative HTML presentation:
  https://www.icann.org/sites/default/files/lgr/rz-lgr-5-khmer-script-26may22-en.html
[RZ-LGR-6-Overview]
  Integration Panel, “Root Zone Label Generation Rules (RZ LGR-6): Overview and Summary”, 23 September 2025,
  https://www.icann.org/sites/default/files/lgr/rz-lgr-6-overview-23sep25-en.pdf
[RZ-LGR-6]
  Integration Panel, “Root Zone Label Generation Rules (RZ-LGR-6)”, 23 September 2025 (XML),
  https://www.icann.org/sites/default/files/lgr/rz-lgr-6-common-23sep25-en.xml
  non-normative HTML presentation:
  https://www.icann.org/sites/default/files/lgr/rz-lgr-6-common-23sep25-en.html
[Unicode 16.0.0]
  The Unicode Consortium. The Unicode Standard, Version 16.0.0, (South San Francisco: The Unicode Consortium, 2024. ISBN 978-1-936213-34-4)
  https://www.unicode.org/versions/Unicode16.0.0/

For references consulted, particularly in designing the repertoire for the Khmer script for the Root Zone, please see details in the Table of References below. Reference [3] refers to the Unicode Standard version in which the corresponding code points were initially encoded. References [100], [203], [204], [205], [206], [207], [208], [209] & [210] correspond to sources justifying the inclusion of or classification for the corresponding code points. Entries in the table may have multiple source reference values.

# Repertoire

## Repertoire Summary

Number of elements in repertoire | 74
Number of code points | 72
Number of sequences | 2
Longest code point sequence | 2

## Repertoire by Code Point

The following table lists the repertoire by code point (or code point sequence). The data in the Script and Name column are extracted from the Unicode character database. Where a comment in the original LGR is equal to the character name, it has been suppressed.

For any code point or sequence for which a variant is defined, additional information is provided in the Variants column. See also the legend provided below the table.

Code Point | Glyph | Script | Name | Ref | Tags | Required Context | Variants | Comment
--- | --- | --- | --- | --- | --- | --- | --- | ---
U+1780 | ក | Khmer | KHMER LETTER KA | [3], [203], [205] | consonant, series-four, series-three |  |  | Khmer
U+1781 | ខ | Khmer | KHMER LETTER KHA | [3], [203] | consonant |  |  | Khmer
U+1782 | គ | Khmer | KHMER LETTER KO | [3], [203] | consonant |  |  | Khmer
U+1783 | ឃ | Khmer | KHMER LETTER KHO | [3], [203] | consonant |  |  | Khmer
U+1784 | ង | Khmer | KHMER LETTER NGO | [3], [203], [205], [210] | consonant, series-three, series-two |  |  | Khmer
U+1785 | ច | Khmer | KHMER LETTER CA | [3], [203], [205] | consonant, series-three |  |  | Khmer
U+1786 | ឆ | Khmer | KHMER LETTER CHA | [3], [203] | consonant |  |  | Khmer
U+1787 | ជ | Khmer | KHMER LETTER CO | [3], [203] | consonant |  |  | Khmer
U+1788 | ឈ | Khmer | KHMER LETTER CHO | [3], [203] | consonant |  |  | Khmer
U+1789 | ញ | Khmer | KHMER LETTER NYO | [3], [203], [205], [210] | consonant, series-three, series-two |  |  | Khmer
U+178A | ដ | Khmer | KHMER LETTER DA | [3], [203] | consonant, series-four |  |  | Khmer
U+178B | ឋ | Khmer | KHMER LETTER TTHA | [3], [203] | consonant |  |  | Khmer
U+178C | ឌ | Khmer | KHMER LETTER DO | [3], [203] | consonant |  |  | Khmer
U+178D | ឍ | Khmer | KHMER LETTER TTHO | [3], [203] | consonant |  |  | Khmer
U+178E | ណ | Khmer | KHMER LETTER NNO | [3], [203] | consonant |  |  | Khmer
U+178F | ត | Khmer | KHMER LETTER TA | [3], [203], [205] | consonant, series-three |  |  | Khmer
U+1790 | ថ | Khmer | KHMER LETTER THA | [3], [203] | consonant |  |  | Khmer
U+1791 | ទ | Khmer | KHMER LETTER TO | [3], [203] | consonant |  |  | Khmer
U+1792 | ធ | Khmer | KHMER LETTER THO | [3], [203] | consonant |  |  | Khmer
U+1793 | ន | Khmer | KHMER LETTER NO | [3], [203], [205] | consonant, series-four, series-three |  |  | Khmer
U+1794 | ប | Khmer | KHMER LETTER BA | [3], [203], [205], [210] | consonant, series-one, series-three, series-two |  |  | Khmer
U+1795 | ផ | Khmer | KHMER LETTER PHA | [3], [203] | consonant |  |  | Khmer
U+1796 | ព | Khmer | KHMER LETTER PO | [3], [203] | consonant |  |  | Khmer
U+1797 | ភ | Khmer | KHMER LETTER PHO | [3], [203] | consonant |  |  | Khmer
U+1798 | ម | Khmer | KHMER LETTER MO | [3], [203], [210] | consonant, series-two |  |  | Khmer
U+1799 | យ | Khmer | KHMER LETTER YO | [3], [203], [210] | consonant, series-two |  |  | Khmer
U+179A | រ | Khmer | KHMER LETTER RO | [3], [203], [210] | consonant, series-two |  |  | Khmer
U+179B | ល | Khmer | KHMER LETTER LO | [3], [203], [205] | consonant, series-three |  |  | Khmer
U+179C | វ | Khmer | KHMER LETTER VO | [3], [203], [210] | consonant, series-two |  |  | Khmer
U+179F | ស | Khmer | KHMER LETTER SA | [3], [203], [205], [210] | consonant, series-one, series-three |  |  | Khmer
U+17A0 | ហ | Khmer | KHMER LETTER HA | [3], [203], [210] | consonant, series-four, series-one |  |  | Khmer
U+17A1 | ឡ | Khmer | KHMER LETTER LA | [3], [203] | base-only, consonant |  |  | Khmer
U+17A2 | អ | Khmer | KHMER LETTER QA | [3], [203], [210] | consonant, series-one |  |  | Khmer
U+17A5 | ឥ | Khmer | KHMER INDEPENDENT VOWEL QI | [3], [206] | independent-vowel |  |  | Khmer
U+17A6 | ឦ | Khmer | KHMER INDEPENDENT VOWEL QII | [3], [206] | independent-vowel |  |  | Khmer
U+17A7 | ឧ | Khmer | KHMER INDEPENDENT VOWEL QU | [3], [206] | independent-vowel |  |  | Khmer
U+17AA | ឪ | Khmer | KHMER INDEPENDENT VOWEL QUUV | [3], [206] | independent-vowel |  |  | Khmer
U+17AB | ឫ | Khmer | KHMER INDEPENDENT VOWEL RY | [3], [206] | independent-vowel |  |  | Khmer
U+17AC | ឬ | Khmer | KHMER INDEPENDENT VOWEL RYY | [3], [206] | independent-vowel |  |  | Khmer
U+17AD | ឭ | Khmer | KHMER INDEPENDENT VOWEL LY | [3], [206] | independent-vowel |  |  | Khmer
U+17AE | ឮ | Khmer | KHMER INDEPENDENT VOWEL LYY | [3], [206] | independent-vowel |  |  | Khmer
U+17AF | ឯ | Khmer | KHMER INDEPENDENT VOWEL QE | [3], [206] | independent-vowel |  |  | Khmer
U+17B0 | ឰ | Khmer | KHMER INDEPENDENT VOWEL QAI | [3], [206] | independent-vowel |  |  | Khmer
U+17B1 | ឱ | Khmer | KHMER INDEPENDENT VOWEL QOO TYPE ONE | [3], [206] | independent-vowel |  |  | Khmer
U+17B3 | ឳ | Khmer | KHMER INDEPENDENT VOWEL QAU | [3], [206] | independent-vowel |  |  | Khmer
U+17B6 | ា | Khmer | KHMER VOWEL SIGN AA | [3], [204] | dependent-vowel, dependent-vowel-1 | follows-consonant-robat-shifter |  | Khmer
U+17B7 | ិ | Khmer | KHMER VOWEL SIGN I | [3], [204] | dependent-vowel, dependent-vowel-2, dependent-vowel-3 | follows-consonant-robat-shifter |  | Khmer
U+17B8 | ី | Khmer | KHMER VOWEL SIGN II | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17B9 | ឹ | Khmer | KHMER VOWEL SIGN Y | [3], [204] | dependent-vowel, dependent-vowel-2 | follows-consonant-robat-shifter |  | Khmer
U+17BA | ឺ | Khmer | KHMER VOWEL SIGN YY | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17BB | ុ | Khmer | KHMER VOWEL SIGN U | [3], [204] | dependent-vowel, dependent-vowel-1, dependent-vowel-2 | follows-consonant-robat-shifter |  | Khmer
U+17BC | ូ | Khmer | KHMER VOWEL SIGN UU | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17BD | ួ | Khmer | KHMER VOWEL SIGN UA | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17BE | ើ | Khmer | KHMER VOWEL SIGN OE | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17BF | ឿ | Khmer | KHMER VOWEL SIGN YA | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17C0 | ៀ | Khmer | KHMER VOWEL SIGN IE | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17C1 | េ | Khmer | KHMER VOWEL SIGN E | [3], [204] | dependent-vowel, dependent-vowel-2 | follows-consonant-robat-shifter |  | Khmer
U+17C2 | ែ | Khmer | KHMER VOWEL SIGN AE | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17C3 | ៃ | Khmer | KHMER VOWEL SIGN AI | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17C4 | ោ | Khmer | KHMER VOWEL SIGN OO | [3], [204] | dependent-vowel, dependent-vowel-2 | follows-consonant-robat-shifter |  | Khmer
U+17C5 | ៅ | Khmer | KHMER VOWEL SIGN AU | [3], [204] | dependent-vowel | follows-consonant-robat-shifter |  | Khmer
U+17C6 | ំ | Khmer | KHMER SIGN NIKAHIT | [3], [204] | sign | follows-consonant-depvowel-1-shifter |  | Khmer
U+17C7 | ះ | Khmer | KHMER SIGN REAHMUK | [3], [208] | sign | follows-consonant-depvowel-2-shifter |  | Khmer
U+17C8 | ៈ | Khmer | KHMER SIGN YUUKALEAPINTU | [3], [207], [208], [209] | sign | follows-consonant |  | Khmer
U+17C9 | ៉ | Khmer | KHMER SIGN MUUSIKATOAN | [3], [207], [208], [209], [210] | shifter | follows-series-two-or-subscript-consonant |  | Khmer
U+17CA | ៊ | Khmer | KHMER SIGN TRIISAP | [3], [207], [208], [209], [210] | shifter | follows-series-one-or-subscript-consonant |  | Khmer
U+17CB | ់ | Khmer | KHMER SIGN BANTOC | [3], [205], [207], [208], [209] | sign | follows-series-three |  | Khmer
U+17CC | ៌ | Khmer | KHMER SIGN ROBAT | [3], [207], [208], [209] | robat | follows-consonant |  | Khmer
U+17CD | ៍ | Khmer | KHMER SIGN TOANDAKHIAT | [3], [207], [208], [209] | sign | follows-consonant-or-vowel-i |  | Khmer
U+17CF | ៏ | Khmer | KHMER SIGN AHSDA | [3], [211] | sign | follows-series-four |  | Khmer
U+17D0 | ័ | Khmer | KHMER SIGN SAMYOK SANNYA | [3], [207], [208], [209] | sign | follows-consonant-shifter |  | Khmer
U+17D2 | ្ | Khmer | KHMER SIGN COENG | [3], [100] | coeng | coeng-context |  | Khmer
U+17D2 U+178A | ្ដ | {Khmer} | KHMER CONSONANT SIGN COENG DA | [3] | [coeng] + [consonant, series-four] | follows-consonant | set 1 | Khmer
U+17D2 U+178F | ្ត | {Khmer} | KHMER CONSONANT SIGN COENG TA | [3] | [coeng] + [consonant, series-three] | follows-consonant | set 1 | Khmer

Legend

Throughout this document, a code point sequence may be annotated with a string in ALL CAPS that is constructed on the same principle as a name for a Unicode Named Sequence. No claim is made that a sequence thus annotated is in fact a named sequence, nor that the annotation in such case actually corresponds to the formal name of a named sequence.

Code Point
  A code point or code point sequence.
Glyph
  The shape displayed depends on the fonts available to your browser.
Script
  Shows the script property value from the Unicode Character Database. Combining marks may have the value Inherited and code points used with more than one script may have the value Common. Sequences are annotated with a set of all distinct script values.
Name
  Shows the character or sequence name from the Unicode Character Database. Named sequences are listed with their normative names, for ad-hoc sequences the individual names are shown separated by “+”.
Ref
  Links to the references associated with the code point or sequence, if any.
Tags
  LGR-defined tag values. Any tags matching the Unicode script property are suppressed in this view. For sequences, the tags for all member code points are shown in [] for information; sequences as such do not have tags.
Required Context
  Link to a rule defining the required context a code point or sequence must satisfy. If prefixed by “not:” identifies a context that must not occur.
Variants
  Link to the variant set the code point or sequence is a member of, except where a coded point or sequence maps only to itself, in which case the type of that mapping is listed.
Comment
  The comment as given in the XML file. However, if the comment for this row consists only of the code point or sequence name, it is suppressed in this view. By convention, comments starting with “=” denote an alias. If present, the symbol ⍟ marks a default item shared among a set of LGRs.

# Variants

## Variant Set Summary

Number of variant sets | 1
Largest variant set | 2
Variants by Type |
blocked | 2

## Variant Sets

The following tables list all variant sets defined in this LGR, except for singleton sets. Each table lists all variant mapping pairs of the set; one per row. Mappings are assumed to be symmetric: each row documents both forward (→) and reverse (←) mapping directions. In each table, the mappings are sorted by Source value in ascending code point order; shading is used to group mappings from the same source code point or sequence.

Where the type of both forward and reverse mappings are the same, a single value is given in the Type column; otherwise the types for forward and reverse mappings, as well as comments and references, are listed above one another. For summary counts, both forward and reverse mappings are always counted separately.

In any LGR with variant specifications that are well behaved, all members within each variant set are defined as variants of each other; the mappings in each set are symmetric and transitive; and all variant sets are disjoint.

Common Legend

Source
  By convention, the smaller of the two code points in a variant mapping pair.
Target
  By convention, the larger of the two code points in a variant mapping pair.
Glyph
  The shape displayed for source or target depends on the fonts available to your browser.
→ - forward
  Indicates that Type, Ref and Comment apply to the mapping from source to target.
← - reverse
  Indicates that Type, Ref and Comment apply to the reverse mapping from target to source.
↔ - both
  Indicates that Type, Ref and Comment apply to both forward and reverse mapping.
Type
  The type of the variant mapping, including predefined variant types such as “allocatable” and “blocked”; or any that are defined specifically for this LGR.
Ref
  One or more reference IDs (optional). A “/” separates references for reverse / forward mappings, if different.
Comment
  A descriptive comment (optional). A “/” separates comments for reverse / forward mappings, if different.

### Variant Set 1 — 2 Members

Source | Glyph | Target | Glyph |  | Type | Ref | Comment
--- | --- | --- | --- | --- | --- | --- | ---
17D2 178A | ្ដ | 17D2 178F | ្ត | ↔ | blocked |  | Khmer subscript form homoglyph

# Classes, Rules and Actions

## Character Classes

Number of named classes | 11
Implicit (except script) | 5
Implicit defined by script tag | 1

The following table lists all named and implicit classes with their definition and a list of their members intersected with the current repertoire (for larger classes, this list is elided).

Name | Definition | Count | Members or Ranges | Ref | Comment
--- | --- | --- | --- | --- | ---
consonant | Tag=consonant | 33 | {1780-179C 179F-17A2} |  | Any Khmer consonant
consonant-but-not-base-only | combined = [[:consonant:] ∖ [:base-only:]] | 32 | {1780-179C 179F-17A0 17A2} |  | Any Khmer consonant that is not base-only
dependent-vowel-1 | Tag=dependent-vowel-1 | 2 | {17B6 17BB} |  | Dependent Khmer vowels used with NIKAHIT
dependent-vowel-2 | Tag=dependent-vowel-2 | 5 | {17B7 17B9 17BB 17C1 17C4} |  | Dependent Khmer vowels used with REAHMUK
dependent-vowel-3 | Tag=dependent-vowel-3 | 1 | {17B7} |  | Dependent Khmer vowel used with TOANDAKHIAT
robat | Tag=robat | 1 | {17CC} |  | Khmer ROBAT
series-one | Tag=series-one | 4 | {1794 179F-17A0 17A2} |  | Khmer consonants used with MUUSIKATOAN
series-three | Tag=series-three | 9 | {1780 1784-1785 1789 178F 1793-1794 179B 179F} |  | Khmer consonants used with BANTOC
series-two | Tag=series-two | 7 | {1784 1789 1794 1798-179A 179C} |  | Khmer consonants used with TRIISAP
shifter | Tag=shifter | 2 | {17C9-17CA} |  | Any Khmer shifter (MUUSIKATOAN or TRIISAP)
series-four | Tag=series-four | 4 | {1780 178A 1793 17A0} |  | Khmer consonants used with AHSDA
implicit | Tag=base-only | 1 | {17A1} |  | The character tagged as base-only
implicit | Tag=coeng | 1 | {17D2} |  | The character tagged as coeng
implicit | Tag=dependent-vowel | 16 | {17B6-17C5} |  | Any character tagged as dependent-vowel
implicit | Tag=independent-vowel | 12 | {17A5-17A7 17AA-17B1 17B3} |  | Any character tagged as independent-vowel
implicit | Tag=sign | 7 | {17C6-17C8 17CB 17CD 17CF-17D0} |  | Any character tagged as sign
implicit | Tag=sc:Khmr | 72 | {1780-179C 179F-17A2 17A5-17A7 17AA-17B1 17B3 17B6-17CD 17CF-17D0 17D2} |  | Any character tagged as Khmer

Legend

Members or Ranges
  Lists the members of the class as code points (xxx) or as ranges of code points (xxx-yyy). Any class too numerous to list in full is elided with "...".
Tag=ttt
  A named or implicit class defined by all code points that share the given tag value (ttt).
Implicit
  An anonymous class implicitly defined based on tag value and for which there is no named equivalent.
Combined
  A named class defined by set operations on other classes using the following syntax:
[: :] - named or implicit character set
  Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.
∪, ∩, ∖, ∆ - set operators
  Sets may be combined by set operators (∪ = union, ∩ = intersection, ∖ = difference, ∆ = symmetric difference).

## Whole Label Evaluation and Context Rules

Number of rules | 15
Used to trigger actions | 3
Used as context rule (C) | 11
Anchored context rules | 11
Used only in another rule | 1

The following table lists all named rules defined in the LGR and indicates whether they are used as trigger in an action or as context (when or not-when) for a code point or variant.

Name | Regular Expression | Used as Trigger | Anchor | Used as Context | Ref | Comment
--- | --- | --- | --- | --- | --- | ---
leading-combining-mark | `(start)[[\p{gc=Mn}] ∪ [\p{gc=Mc}]]` | ✔ |  |  |  | Default WLE rule matching labels with leading combining marks ⍟
subscript-consonant | `\u17D2[:consonant-but-not-base-only:]` |  |  |  |  | WLE Rule 2: allowable subscript consonant sequence
subscript-consonant-limit | `(:subscript-consonant:){3,3}` | ✔ |  |  |  | WLE Rule 3: more than two subscript consonants
coeng-after-subscript-ro | `\u17D2\u179A\u17D2` | ✔ |  |  |  | subscript RO must be last in a syllable
coeng-context | `([:consonant:])← ⚓︎ →([:consonant-but-not-base-only:])` |  | ✔ | C |  | WLE Rule 4: checks for 17D2 and its surrounding code points
follows-consonant-robat-shifter | `([:shifter:]|[:consonant:]|[:robat:])← ⚓︎` |  | ✔ | C |  | WLE Rule 5: makes sure that dependent vowel follows a consonant or a shifter or a robat
follows-series-two-or-subscript-consonant | `([:series-two:]|(:subscript-consonant:))← ⚓︎` |  | ✔ | C |  | WLE Rule 6: checks sequence for shifter 17C9 MUUSIKATOAN
follows-series-one-or-subscript-consonant | `([:series-one:]|(:subscript-consonant:))← ⚓︎` |  | ✔ | C |  | WLE Rule 7: checks sequence for shifter 17CA TRIISAP
follows-consonant | `([:consonant:])← ⚓︎` |  | ✔ | C |  | WLE Rule 8: checks if sign code point or subscript consonant follows a consonant
follows-consonant-shifter | `([:consonant:]|[:shifter:])← ⚓︎` |  | ✔ | C |  | WLE Rule 9: checks if 17D0 KHMER SIGN SAMYOKSANNYA follows a consonant or a shifter
follows-consonant-depvowel-1-shifter | `([:consonant:]|[:dependent-vowel-1:]|[:shifter:])← ⚓︎` |  | ✔ | C |  | WLE Rule 10: checks if 17C6 KHMER SIGN NIKAHIT follows a consonant or a dependent vowel-1 or a shifter
follows-consonant-depvowel-2-shifter | `([:consonant:]|[:dependent-vowel-2:]|[:shifter:])← ⚓︎` |  | ✔ | C |  | WLE Rule 11: checks if 17C7 KHMER SIGN REAHMUK follows a consonant or a dependent vowel-2 or a shifter
follows-series-three | `([:series-three:])← ⚓︎` |  | ✔ | C |  | WLE Rule 12: checks if 17CB KHMER SIGN BANTOC code point follows a series-three consonant
follows-consonant-or-vowel-i | `([:consonant:][:dependent-vowel-3:]?)← ⚓︎` |  | ✔ | C |  | WLE Rule 13: checks if 17CD KHMER SIGN TOANDAKHIAT follows a consonant or 17B7 KHMER VOWEL SIGN I (Dependent-vowel-3)
follows-series-four | `([:series-four:])← ⚓︎` |  | ✔ | C |  | checks if 17CF KHMER SIGN AHSDA follows a series-four consonant

Legend

Used as Trigger
  This rule triggers one of the actions listed below.
Used as Context
  This rule defines a required or prohibited context for a code point C or variant V.
Anchor
  This rule has a placeholder for the code point for which it is evaluated.
Regular Expression
  A regular expression equivalent to the rule, shown in a modified notation as noted:
⚓︎ - context anchor
  Placeholder for the actual code point when a context is evaluated. The code point must occur at the position corresponding to the anchor. Rules containing an anchor cannot be used as triggers.
(...)← - look-behind
  If present encloses required context preceding the anchor.
→(..) - look-ahead
  If present encloses required context following the anchor.
(: :) - rule reference
  Non-recursive reference to a named rule.
(... | ...) - choice
  When there is more than one alternative in a rule, the choices are separated by the alternation operator (...|...).
start or end
  (start) matches the start of the label; (end) matches the end of the label.
*, +, ?, {n,m} - count operators
  * indicates 0 or more, + indicates one or more, and ? indicates up to one instance. {n,m} indicates at least n and at most m instances.
[: :] - named or implicit character set
  Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.
[\p{ }] - property
  Set of all characters matching a given value for a Unicode property [\p{prop=val}]. Note: uppercase “\P” defines the complement of a property set.
∪, ∩, ∖, ∆ - set operators
  Sets may be combined by set operators (∪ = union, ∩ = intersection, ∖ = difference, ∆ = symmetric difference).
⍟ - default rule
  Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

## Actions

The following table lists the actions that are used to assign dispositions to labels and variant labels based on the specified conditions. The order of actions defines their precedence: the first action triggered by a label is the one defining its disposition.

# | Condition | Rule / Variant Set |  | Disposition | Ref | Comment
--- | --- | --- | --- | --- | --- | ---
1 | if label matches | leading-combining-mark | → | invalid |  | labels with leading combining marks are invalid ⍟
2 | if at least one variant is in | {out-of-repertoire-var} | → | invalid |  | any variant label with a code point out of repertoire is invalid ⍟
3 | if label matches | subscript-consonant-limit | → | invalid |  | any label with more than two subscript consonants in a row is invalid
4 | if label matches | coeng-after-subscript-ro | → | invalid |  | subscript RO must be last in syllable
5 | if at least one variant is in | {blocked} | → | blocked |  | any variant label containing blocked variants is blocked ⍟
6 | if each variant is in | {allocatable} | → | allocatable |  | variant labels with all variants allocatable are allocatable ⍟
7 | if any label (catch-all) |  | → | valid |  | catch all (default action) ⍟

Legend

{...} - variant type set
  In the “Rule/Variant Set” column, the notation {...} means a set of variant types.
⍟ - default action
  Actions marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: allocatable, out-of-repertoire-var. This is not necessarily an error.

# Table of References

The following lists the references cited for specific code points, variants, classes, rules or actions in this LGR. For General references refer to the References section in the Description.

[3] | The Unicode Standard, Version 3.1 Any code point originally encoded in Unicode Version 3.0
[100] | The Unicode Consortium. The Unicode Standard, Version 8.0.0, (Mountain View, CA: The Unicode Consortium, 2015. ISBN 978-1-936213-10-8), Chapter 16: Southeast Asia, Section 16.4: Khmer, https://www.unicode.org/versions/Unicode8.0.0/ch16.pdf Subsection, Subscript Consonant Signs, pages 616-618
[203] | PRIMARY SCHOOL GRADE 1, MOEYS, ISBN 9-789-995-001-674, Publication 2015, Figure 1 Any code point cited is for consonant characters
[204] | PRIMARY SCHOOL GRADE 1, MOEYS, ISBN 9-789-995-001-674, Publication 2015, Figure 2 Any code point cited is for vowel signs
[205] | Dr. Prum Mol (Khmer Linguist), Grammar of Modern Khmer Language, Linguist of National Institute of Language, Royal Academy of Cambodia, 2006, page 37 Bantoc sign section starts towards the bottom of the page, page 38 list the context of the Bantoc sign BANTOC sign and its context
[206] | PRIMARY SCHOOL GRADE 1, MOEYS, ISBN 9-789-995-001-674, Publication 2015, Figure 6 Any code point cited is for independent vowel characters
[207] | PRIMARY SCHOOL GRADE 1, MOEYS, ISBN 9-789-995-001-674, Publication 2015, Figure 7 Any code point cited is for diacritics
[208] | PRIMARY SCHOOL GRADE 1, MOEYS, ISBN 9-789-995-001-674, Publication 2015, Figure 8 Any code point cited is for diacritics
[209] | PRIMARY SCHOOL GRADE 1, MOEYS, ISBN 9-789-995-001-674, Publication 2015, Figure 9 Any code point cited is for diacritics
[210] | Franklin E. Huffman, Cambodian System of Writing and Beginning Reader, Yale University, 1970, reprinted 1987 Sets of code points used with certain signs
[211] | Root Zone Label Generation Rules Version 6 (RZ-LGR-6) Submission - Sok, Makara, 29 July 2025 https://www.icann.org/en/public-comment/proceeding/root-zone-label-generation-rules-version-6-rz-lgr-6-17-06-2025/submissions/sok-makara-29-07-2025 Code point added as result of public comment